I am an owner-builder trying to come up with some HVAC specifications for a house presently under design. I will use a general contractor on a lump sum basis to keep me out of too much trouble.
I am located in western NC in lower mtns. (1500 ft.) I expect to be going with either a 12+ seer 2-speed heat exchanger with dampeners or two separate units. Figure 2600 ft. 1st. floor and 1000 ft second fl. Second floor will see very little use. Have not decided to use foam insulation or not. Will go all electric which is pretty cheap here. Gas for cook top and fireplace only. Do expect to have minor heat/air circulation in the basement/crawlspace and attic areas not otherwise used for living space. (sounds like two units is the way to go after reading what I wrote but if it is two speeds with electric dampeners big savings I would think– though relying on electric dampeners I can’t otherwise reach sounds like a bad idea…).
I Would reallllly appreciate any consensus (yea right) as to equipment, round-flex ducts, makeup air, furnace location, HEPA filter system and well, specifications for all the trades, e.g., the rest of the house… Spent hundreds of hours trying to build a house spec-book and this is the best forum I have found. Thanks for any help — anyone.
EMS
Replies
First of all, since it seems that this is your first post, Welcome to Breaktime!
Second, it seems that you have narrowed your choice down to a forced air system. If that is the case, great, though many will try to convince you that radiant infloor heat is the way to go. Either way, you asked for some input on some specifics. You will get many opinions, some based on a great deal of experience, some based on nonsense.
The manufacturer of the equipment is of secondary concern (although there are dozens of brands, there are only 5 manufacturers of residential equipment in the US). You need to "specify" what you want interms of features and installation.
Given the size and square footage you mentioned, I would go with two units, one for each floor.
The air handler/electric "furnace"/evaporator coil - features to look for are: variable speed blower, multiple stages of heat, foil faced insulaion or double-walled insulated cabinet, built-in evap coil with factory TXV.
The AC unit (condenser) will most likely be 13 SEER or greater - features to look for: high and low pressure switches, scroll compressor, liquid line filter-drier, factory time delay, sturdy coil guard, brass service valves.
Media filter - my preference is this over an electronic - features, 4 or 5" thick MERV 11 filter element, no more that 500 fpm face velocity, "dirty filter" indicator.
Makeup air - 6" Skuttle for basic fresh air/MA.
Installation - all joints tapes or sealed with mastic, no flex, volume dampers in all branch ducts, ducts sized to no more than 0.1"/100 ft static pressure drop for trunk lines, 0.08"/100 ft branches and returns, multiple ducted returns (i.e. no single central return) no flex ducts. The location will depend on the layout of the home, but central locations with equal branches is best.
Thermostat - hardwired, two stage, programmable with battery backup
Additionally, unless you plan to perform the load analysis your self and specify capacities as well as features, require that any hvac contractor provide a detailed load calculation for each floor, heating and cooling.
Wow. Great help. Why not Flex ducts?
For compressors is the Copeland Scroll compressor the current state of the art? Would you recommend the Vision Pro from Honeywell or White-Rodgers thermostat?
You don't think one 3-4-zone Evolution system from Bryant is not a good way to go instead of two units? It is hard to tell which HVAC subs will be selling product they want to sell and who sells what I should buy...
considering the total cost of two smaller units and less complicated runs, maybe two units will work out better I suppose.
EMS
Flex ducts when installed properly and per SMACNA recommendations are acceptable in limited use. The problems with flex is that it is very easy to install poorly, has greater resistance to flow than sheet metal ducts, it is most attractive to use in confined/cramped spaces when it is most likely to be crimped, crushed or distorted. It is very susceptible to physical damage. To save the aggravation of how much is too much?, I say none.
I sell both White-Rodgers and Honeywell and have a Honeywell VisionPro in my home. Ilike the way they look as compared to W-R.
Copeland scrolls are about as good as any other and a lot of manufacturers use them. Scroll compressors are quieter, typically, than recip's, and also tend to last longer.
IF I were to zone a residential forced air system, I would go with the Honeywell EnviraZone system, however there are several issues with a simple zoned system (all resonably priced systems for this type of application ARE simple). You or your contractor has to be pretty sharp with duct design and plan well. The cost of a big zoned system good enough to work well is not going to be less expensive than multiple systems (in commercial HVAC design, the break even point when going from multiple packaged units to a larger zoned unit was about 5 or 6). The duct runs for two smaller systems will be simpler and smaller, and overall should be less expensive. You also have the extra safety factor of some redundency. One unit fails in the middle of the night when it's 10 below and snow is blowing, has all the roads to your mountain hideaway blocked, you still have an operating system.
As far as one brand vs. another, I have no preference or recommendation. The best equipment available installed poorly will be dissappointing. The least expensive equipment available installed by a quality professional will provide years of trouble free comfort. Bryant is Carrier. Amercian Standard is Trane. Coleman is Luxaire is York. Keeprite is Heil is ICP. Most installers/dealers handle multiple brands. They will obviously push the more expensive brands because those have great name recognition and that is how/why they advertise.
If you want to find out how good the various contractors are ask them some questions.
Will you use flex duct? Why or why not? (see above) How did you determine the size(s) of the equipment? How long have you been in this business. Are you NATE certified? How long will you warranty your installation? How much will you charge me for service calls in the first year? Can I have a list of your last 20 customers? How much should I expect in utility bills?
Not all of the questions have right or wrong answers. But the answers are important. Get a list of references and call them.
To some this may seem unnecessary, but I have seen far too many porly installed systems out there to believe that you can get a good one by chance. Weed out and rule out the hacks. The reason so many people think that their forced air system is terrible is because its true. Not that the equipment is inadequate, just the majority are poorly installed.
On hvac, get the phone book, find the biggest oufit with the most employees and most trucks, find one that say something like "Since 1949"
these will be your hometown boys, they have a reputation and want to keep a reputation. they will be in business twenty years from now. They will be high price, but you are paying for service. They will have good equipment. proberly bryant or rheem, a well know brand.Tell them what you want and let them do it. you are not paying for brand but service. In the hvac trade, there is a lot of fly by night that will only be in business couple years. maybe two or three guys. when a business goes out so does the warrenty. On hvac, I will not do business with anybody without at least thirty employees.you are paying for service and somebody that will come out at night, on weekends, holiday. somebody who can afford to keep a van with parts. If you bid it, throw out the bottom ten bids, and take the highest.. 2+3=7
I hear ya. Getting the same from others as you see. It is so nice to have all this backstop to questions that have an affect on daily life as in HVAC. Thank you very much for our informed reply. I shall follow the advice.
EMS
Wow again. You are writing a 'How-To' book here. I should let you negotiate this. I can't wait to get my list together. I'm afraid I'll ask a 'bright' question then look like a deer in the headlights when the answer comes back...
Now, how important that the HVAC person gets involved with the structure design e.g., the joist/truss systems before that is finalized? I know ideally each trade and the homeowner would like a crack at making their job easier and a better; and by having other trades think of how the framing/ducts/wiring/plumbing/finishing etc. will work together.
How often do plans get offered to the trades for comments before they are finalized. I'll bet seldom to never but it sure seems like a smart thing to do. Designers and the 'dooers' are often at odds when it comes to practice.
OK, two systems. One-system with zones would require expertise I may not find too close by (our entire county (Polk) here in NC has only 5 traffic lights if that is any clue to the population) and find the best/oldest/largest I can locate with your specs. This is so helpful. Your posts will be cited as athourity frequently I would think.
EMS
I'm a homeowner, we're building a house and haven't had a pleasant experience with our HVAC contracter. We're putting in geothermal, so we had a limited choice in our area.Make sure to specify that you want your returns ducted throughout--they were stunned that I didn't want panned returns. However, didn't find out they were panning them until they were working. Getting them done required a change order and more money since they've never done that before. Be sure to specify that all the seams need to be sealed with tape or mastic.Definitely try to get some input in the planning stages. We tried unsucessfully--mostly they just complained about our open floor plan--but never gave us size requirements for the ducting they needed to install even though we asked so that we could incoporate it into our plans. So we ended up with a tortuous path through the framing--which we could have avoided with their input. I would definitely recommend getting their input on your plans as early as possible. Insist on a trip to the site BEFORE they come to rough in to plan out the ductwork with you.Good luck
Jo
"Now, how important that the HVAC person gets involved with the structure design e.g., the joist/truss systems before that is finalized?"
Integrating the ductwork into the structure is usually done as an afterthought in residential construction. As someone who has done designs in both commercial/institutional buildings as well as a few residential systems, the practice of involving the MEP (mechanical, electrical, plumbing) trades as early as possible helps. In commercial jobs, it is critical.
IF you had the opportunity to influence the structural design to accomodate HVAC and plumbing, between the first and second floor use wood trusses in leiu of truss-joists. That way ducts and pipes can be run between floors and not in unconditioned spaced like the attic (never recommend if you can avoid doing so). This is what I did when I added on to my home. Most of the ducts serving the second floor are located in between floors.
BTW, you don't have to have two systems or a zoned system. I have a single gas furnace that handles over 5000 sf of conditioned space, (counting the basement). In the summer, I close or partially close the registers on the lower levels and open up on the second floor. In the winter, I do the opposite. I heat from the bottom up and cool from the top down. It takes less tome to close a few registers than it took to type this message, but I type slowly.
Asking questions of the contractors is not necessary. Just compare apples to apples and you'll have good comparisons.
Tim, why two units? You can buy units to heat 4000 sq ft or more, no?
Naturally, the advantage would be that you could avoid heating the upstairs as in this case where the poster said it would not get much use. And secondly, it would give you emergency redundancy.
Any other reasons, if those were unimportant?
"Tim, why two units? You can buy units to heat 4000 sq ft or more, no?"
Absolutely, depending on the climate and construction you can have a 6000 sf home served by a single furnace. A large 125,000 btuh input, 94% efficient furnace could easily heat (and does in my case) a large well insulated home even in very cold climates. In warmer regions air conditioning would be a more limiting concern. As I explaind to EMS, the practical reason is for zoning, for ease of installation, and to provide some redundancy. Dividing a house into a couple of zones is easy enough, but the larger sheet metal sizes (like 24x20, etc) are harder to come by and more expensive. Sure you can get 30x8 standard duct, but how are you going to get from the basement to second floor with two of those (or slightly smaller, depending on the specifics of the design). Ultimately one, unzoned system is cheaper that two smaller systems, but it is a compromise.
And if a guy did wish to have a second floor which would seldom be used, would anyone recommend insulation between the floors to further save money on energy consumption?
I guess the sound attenuation would be the only other reason to add the insulation between the floors. I Will carpet the upstairs to keep the noise down though and with the pad maybe that is enough. Besides, the upstairs BRs are not over mine down below.
Any other thoughts out there about ceiling insulation in a two story house? Makes for warm floors upstairs...
EMS
I would recommend insulating between floors for sound control more so than to help with unintended heat migration.
You received some great advice from the others. One thing to add is that some manufacturer's offer two stage heat pump systems. The indoor fan ramps up to a reduced speed for normal cycles and to max speed when the requested temperature setting gets two to three degrees beyond the deadband of the thermostat. The outdoor unit performs similarly by using a two stage compressor (first atage for low demands and both stages for high demands). I installed one 4 years ago and saw a $20.00 reduction in my energy bill the first month (September). The ROI (in the Piedmont of NC) for the premium price was 9 months. A programmable thermostat is well worth the money.
Stay away from fiberglass ductboard for your duct system and keep the indoor unit easily accessible. Crawl spaces for LPG or NG furnaces are not good. The condensate can freeze in the drain lines and the units will not stay on line.
Good luck
Thank you. Yes, two stage is the way to go down stairs. Up stairs will get so little use...we shall see what makes sense. I will be going all electricity heat pump here in NC lower mountains. Cheaper than NG.
Next question will be about installing an LEV elevator system or at least the shaft for the car installation later/next owner. I'm into the 'universal design' these days...
EMS
A couple of other things based on my recent experience. If you can find a third party to test your system after installation with a "duct blaster" test, it'll show you how much leakage you have in both the supply and return ducting. A good criteria to use for your maximum leakage is 0.05 cfm/sq ft interior space.
One thing this will probably force that I think most HVAC companies don't address is that register boots in ceilings aren't typically sealed to the drywall. During the test, sticky wrap goes over the registers, so a non-sealed connection at the drywall will leak.
Ideally, it'd be easier to test before insulating (or at least covering joints). Anyway, putting this stuff in your specs up front and making your expectations clear will save trouble down the road. Plus, make sure that correcting leaky ductwork and costs for re-testing aren't yours to bear.
Thank you. I added that as though I know what I'm talking about. My specs are about 20 pages now and I gave them to a HVAC contractor acquaintance to 'regurgitate' on so we will see what the reactions are. You can have the same laugh -- as I have included them as attachments here. -- or I think I have... I found a lot of interesting specs on a State of CA energy site. It had lots of ideas and reasons for the specs. You can see it at http://www.energy.ca.gov/efficiency/qualityhomes/procedures.html
EMS,
HAH! I got the first critique.
In Special*.doc
Typo in Para #7 = practical vs praticlePara #8; suggest "Building structural members" for clarityPara #10; suggest industry standard term "Contractor" vice unique term "Proposer"Para #11; This is just the contractor side of me, but, why do want to know my labor costs? Are you thinking of shopping my proposal or buying the equipment yourself?
I really like your contract writing style. I am in the middle of writing a 20-30 page contract my self right now. Whew. And whew again.
Hope you will critique my poor efforts when I'm done.
SamT
I will use your comments. Thank you.
I am still in the drafting stage of this and I may change from "Proposer" to "Subcontractor" since I will be the "Contractor-Owner".
I asked to have the equipment and labor broken out to see if I have better sources for equipment pricing and to compare the bids. If one contractor has disproportionate costs either way they may have missed something or found something the others/myself missed. It also allows me to be able to better negotiate among bidders. I think I will also ask for the time expected to perform the work so if there are change orders I have what they bid the labor costs on a per hour basis.
I may also include an add/deduct clause in the general contract that applies to all subcontractors to cover costs for changes in the subcontractor's work. For example, should I decide not to condition the attic space I want to be able to deduct the cost of the labor and equipment in the lump sum contract resulting from that reduction in work. I may also include a savings clause (a/k/a/ Value Engineering) e.g., if the subcontractor comes up with a better way to do something than performing the work the way the contract requires, the subcontractor and owner would share the savings, usually 60% to owner and 40% to subcontractor. That way the subcontractor thinks up ways for him to make 'free' money and me 'free' savings. But hopefully that 'better way' will be presented in the form of an alternative in the bid itself.
EMS
EMS,
I have totally rejected the AIA contract section that relates to Change orders.
Attached is the section I have developed to date. Check it out for ideas you can use.
SamT
You asked how much is it going to operate this system?
IT DEPENDS.
I have read through your documents.
If I was to bid on your work, there is no way I would do all that preliminary work without an acceptance of my bid. Who is going to pay me for my time to design a system to meet all of your requirements- especially if I know you are shopping bids from a half dozen other contractors? Do you work for free?
No way would I give a parts and labor breakdown. If you want the work done, this is the price. No way I would warranty any owner supplied equipment, either. If you want to save money, you engineer it. I would not provide equipment sizes unless the bid is accepted. If you want a "labor only" deal, give me engineered drawings, supply all the material, and you will get a labor only price. Change orders and RFI's would be your problem. I call you when it doesn't fit :) That's how it is in the real world.
If you insisted on a parts and labor breakdown, I would do it just like the builders give their "credits". There is no way that a builders "credit" is going to cover the cost of the item if you sourced it yourself.
Are you willing to pay for the system you are specifying? Are you willing to change the blueprints of the home to allow your duct specifications to work (furred out walls, soffits, a duct chase, etc.)- especially around the other trades? Will the carpenters frame EXACTLY per plan? Are your plans good enough to list from 100% (I have never seen a set that has worked 100% yet)? Is the HVAC duct system designed into the building framing?
A good HVAC contractor can come up with a workable bid number based on the drawings for a basic residential install- which is what all those pages describe. You are not building a 20,000 square foot multimillion dollar estate here.
You are specifying a system done 100% right, which is commendable. I have never met anyone willing to pay for it once the numbers are worked out.
You will be foolish to run gas to the house and not install some type of gas backup. At least then you can run the furnace on a generator.
Lots of luck finding someone to do it all upfront for free.
Edited 1/14/2006 12:28 pm ET by danski0224
If you insisted on a parts and labor breakdown. this is none of your business, I would not bid it.Bid as a turn key job.. 2+3=7